In order to determine a location of a transmitting source, location techniques use the measurements obtained by a plurality of receivers. The obtained measurement data are informative of intensity (signal strength) and/or the phase and/or delay of the transmitted signal, and can be used for estimating distance to the transmitting source in accordance with received signal strength (RSS), time of arrival (TOA) at the receivers, angle of arrival (AOA) of the transmitted signal, time difference of arrival (TDOA) at the receivers, etc.
The location techniques (e.g. radio frequency location) are well-known when assuming free-space propagation, however multipath interference makes the location estimation process to become challenging. Multipath is characterized by multiple reflections, while reflections power and the reflections delays dependent on the nature of the environment.
Problems of mitigating the effects of multipath propagation in location of a transmitting source have been recognized in the conventional art and various techniques have been developed to provide solutions, for example:
U.S. Pat. No. 8,077,091 (Guigne) discloses a method of determining a position of a mobile device within a surveillance volume. The method comprises synchronizing communications between a phase difference array comprising a spatially diverse array of N sensors and the mobile device, N being greater than 4; acquiring phase difference data as a function of time using the phase difference array and determining phase differences for a plurality of receiver pairs defined for the phase difference array, each receiver pair consisting of a unique pair of the sensors in the spatially diverse array of N sensors; and determining the position of the mobile device from the phase differences.
U.S. Patent Application No. 2011/0273328 (Parker) discloses a method of geolocating a moving transmitter observed by a plurality of fixed or nearly fixed receiver devices, and a moving receiver device. The method includes obtaining wavelength-scaled phase difference measurements from the plurality of fixed or nearly fixed receiver devices to obtain a shape of the transmitter trajectory, measuring the phase difference between the moving receiver device and at least one of the plurality of fixed or nearly fixed receiver devices to obtain a phase error residual, and moving an estimated starting point of the transmitter to obtain a best-fit residual.
International Patent Application No. WO15/001552A1 (Boker) discloses a method and system for radiolocation of RF transmitter in the presence of multipath interference. RF receivers are spatially separated at known locations in a moderate multipath environment in the vicinity of the transmitter. Upon detection of a received active RF signal associated with the transmitter, the receivers are directed to acquire measurements of the detected RF signal. Each receiver obtains a sequence of measurements of the RF signal at different positions along a trajectory that provides multiple measurements at relative phase differences between the direct-path and the multipath reflections of the detected RF signal. The receivers may be repositioned automatically or manually, or prearranged or selectively deployed at fixed positions along the trajectory. TDOA measurements between pairs of receivers are calculated based on the obtained measurements, and are averaged to provide a respective updated TDOA measurement value for each receiver pair, which is used to determine the transmitter location.
The references cited above teach background information that may be applicable to the presently disclosed subject matter. Therefore the full contents of these publications are incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background.